1. Field of the Invention
The subject invention relates to a heating, ventilation and air conditioning (HVAC) system of the type including a valve for controlling air flow. More specifically, the HVAC systems include a film valve that is linearly movable for controlling air flow.
2. Description of the Prior Art
These HVAC systems are known in the art for use in vehicles and include a housing defining an air passage for directing air flow through the housing. A valve includes a film having side edges and an opening disposed between the side edges. The film is supported by the housing to extend across the passage for controlling air flow through the passage. The systems include a mechanism for moving the film linearly to block air flow and to allow air flow through the opening in the film. Such mechanisms frequently include a rack extending along the film and having teeth disposed therealong and a sprocket having sprocket teeth engaging the teeth for moving the rack and the film linearly. U.S. Pat. No. 6,669,549 to Uemura et al. discloses an HVAC system as described above.
One of the problems with prior art HVAC systems that include the film is that the housing of the HVAC system is solely relied upon to prevent the film from succumbing to force exerted on the film from the air flow and vibration. More specifically, the film is sandwiched within the housing, which maintains the teeth of the rack in contact with the sprocket. Any misalignment of the film due to catching on the housing, movement within the housing due to air loading, or vibration can cause the teeth to become misaligned with the sprocket. The misalignment may result in excessive noise or, ultimately, loss of valve function.
Thus, there is an opportunity to overcome the deficiencies of the prior art HVAC systems to provide a film and a mechanism for moving the film linearly that is not prone to failure due to misalignment between the teeth and the sprocket.